With popularization of smartphones, and continuous increase in demands of users on high-speed data services, modern mobile communications develop in a multi-frequency and multi-mode direction. However, because it becomes increasingly difficult to acquire resources at an available site and the site raises a higher requirement for integration with an ambient environment, a multi-frequency communications antenna of higher integration becomes a future development direction of a base station antenna.
A multi-frequency communications antenna refers to an antenna that includes multiple antenna arrays that can operate on different frequency bands. Arrangement of multiple antenna arrays that have different frequency bands in limited installation space often results in a significant decrease in electrical performance of each array, such as a horizontal beam width, a cross polarization level, and a front-to-rear ratio, due to relatively strong electromagnetic coupling.
To ensure that the multi-frequency communications antenna still has a good radiation characteristic in a case of high integration, for example, a low-frequency radiation apparatus disclosed in Chinese Patent Application No. 201210319758.21 in the prior art includes a first low-frequency radiation module and a second low-frequency radiation module, where an open-circuit stub for suppressing transmission of a high-frequency electromagnetic wave in the low-frequency radiation apparatus is disposed separately at a side of an axial center of the first low-frequency radiation module and the second low-frequency radiation module, and a coupled current of another frequency is suppressed using the open-circuit stub.
However, disadvantages of the low-frequency radiation apparatus shown in the prior art lie in that: 1. The open-circuit stub is implemented only on a balun by means of sheet-metal working or PCB processing, and is difficult to be implemented by means of die-casting. 2. Even if multiple open-circuit stubs with different lengths are used, a relatively narrow bandwidth can be suppressed. 3. Elimination of a mutual coupling effect is only related to a structural length of the designed open-circuit stub, and multi-frequency mutual coupling and wideband mutual coupling cannot be resolved. 4. A structure of the open-circuit stub that eliminates mutual coupling damages an operating environment of the low-frequency radiation apparatus.